The invention entails a method and related mechanism for the production of methane rich biogas from organic materials, more specifically for the production of biogas with a high methane content. In methods of this kind, the organic matter is decomposed by means of living micro-organisms and converted to methane.
Gas, which can serve as an alternative energy source, is generated in the decomposition of organic substances. For reasons of its generation, this gas is described as biogas. An important component of biogas is methane, which originates from organic or vegetal substances or their by-products through fermentation or decomposition under closure from air. In larger production contexts, it is generated through the gasification of coal or in petrochemical processes and is utilised as heating gas and for combustion power, as well as raw material for synthetic products, such as (inter alia) acetylene, synthetic gas, HCN and chlorine substitute products.
Because of methane""s importance, it is aimed to achieve a high proportion of methane in the production of biogas. Depending on the level of technology, single or double stage fermentation methods are employed, by which biogas with a methane content of between 40% and 60% is generated from organic material through anaerobic fermentation. The remaining biogas components in these processes consist to between 25% and 55% of CO2, as well as of smaller quantities of nitrogen, hydrogen sulphide and other components.
Hitherto known methods of anaerobic fermentation for the generation of methane from organic materials are therefore not completely satisfactory with regard to the quality of biogas and the volumes of methane produced. Particularly undesirable in these processes is the high proportion of approximately 2% sulphur or hydrogen sulphide, because in concentrations from as low as 0.1%, these are troublesome in the operation of engines and the allied engagement of catalytic converters.
In addition, there are further disadvantages related to known methods of anaerobic fermentation. Thus, the degree of decomposition is usually around 45% of the dry organic substance and the production processes are relatively unstable, as the micro-organisms involved therein are sensitive to environmental changes. A further effect of this is that any discontinuities of the process, such as occurs during servicing intervals or repairs and the subsequent resumption of production, means that profitable productivity levels are only attained some 12 to 25 weeks thereafter.
Furthermore, hitherto familiar technologies leave a non-utilisable residue amounting to about 30% to 70% of the input volumes, which must be rendered free of harmful deposits. Similarly, the conversion time, i.e. the duration between the input of the organic materials to the process and the production of biogas, is relatively long and takes in the vicinity of between 20 and 30 weeks.
The known methods are admittedly environmentally neutral with regard to the carbon dioxide economy, however they do not lead to any reduction in the carbon dioxide burden on the environment. It also remains to be considered that the methane from the unmanaged decomposition in nature is 30 times more negatively burdensome for the greenhouse effect than CO2.
U.S. Pat. No. 4,289,625 describes a bio-thermal gasification method whereby organic matter is initially fermented anaerobically and its residue is then carbonised. The gases formed during carbonisation are then converted to methane by means of anaerobic micro-organisms.
Although the known methods are environmentally neutral in terms of the carbon dioxide economy, they do not lead to a reduction of the environment""s carbon dioxide burden. Also to be considered in this regard is the fact that the methane released in the uncontrolled process of decomposition in nature is about 30 times more negatively burdensome than CO2 for the green house effect.
The object of the invention is to provide a method and related mechanism for the production of methane rich biogas from organic materials by means of which living micro-organisms decompose the latter while delivering a higher margin of methane and simultaneously avoiding or reducing the negative side effects of this state of technology.
The foregoing object is achieved by the present invention by providing a method A method for producing biogas containing methane, comprising: a) contacting organic matter with fermentation micro-organisms under anaerobic fermentation conditions so as to produce residuals and gaseous wastes containing carbon dioxide; b) carbonizing the produced residuals to obtain a charcoal product and wood gas; and c) contacting the wood gas with thermophile fermentation micro-organisms under anaerobic fermentation conditions to produce biogas containing methane and mechanisms for carrying out the method.